The present disclosure relates to a power factor correction circuit protecting circuit devices by limiting inrush current occurring at the initial state of AC power connection.
Since the phases of voltage and current are not necessarily equal to each other in an AC circuit, all the products thereof are not becoming actual power to be used. A ratio of the product of voltage and current and active power, i.e., actual power to be used, is referred to as a power factor. If the power factor is small, since that much of transmission power loss occurs, a power factor correction circuit for preventing the loss is widely used for various electronic devices. Additionally, the installation of such a power factor correction circuit becomes mandatory in some countries.
A charging device for charging a battery of an electric vehicle requires a power factor correction circuit. At the initial charging of a battery, since a capacitor of a smoothing unit in a power factor correction circuit is not charged yet, inrush current occurs. The inrush current refers to a flowing current higher than normal current when power is applied to a distribution line or an electronic device. In relation to the inrush current, as soon as power is on, current corresponding to several times or several ten times normal current flows and decreases gradually and then, disappears when a steady state is reached. If such an inrush current flows as it is, current higher than the maximum allowable current of devices in a circuit flows. As result, malfunction and failure may occur. Accordingly, a device for limiting inrush current is required.